It is known that liquid reducing agents are introduced into the exhaust gas flow for treating the exhaust gas. For example, ammonia or urea or an aqueous urea solution can be dosed to the exhaust gas flow upstream of a so-called catalytic converter, which can perform a selective catalytic reduction, in order to decompose nitrogen oxides in the SCR catalytic converter. It is important for the proper and efficient mode of operation of such an SCR catalytic converter or of another means operating with a dosed liquid educt that the most homogeneous mixture of exhaust gas and reducing agent be obtained. Furthermore, possibly extensive or complete evaporation of the educt introduced in the liquid state must be achieved, in addition, in case of certain educts before the mixture enters the means in question, for example, the SCR catalytic converter. It is common practice for this to provide within the respective exhaust gas-treating device a mixing section, which is usually formed by a straight tube, through which the educt-exhaust gas mixture enters a chamber, into which an inlet of the SCR catalytic converter in question or of the treating means in question opens.